1. Field of the Invention
A convertible air cleaner fan unit for desk top use which provides an improved, air purifier/smoke removal device which may be instantly converted to a fan for furnishing a supply of purified and conditioned air to the user. The device improves upon the air flow characteristics of ordinary individual air clearners, and in combination with an integral task light, becomes a unique, useful and compact desk top accessory.
2. Description of the Prior Art
There is much concern being voiced at present about indoor air pollution, deriving primarily from the growing awareness of the danger of cigarette smoking. This concern has expanded to include secondary cigarette smoke, and the outgassing of modern building materials. The problem is particularly acute in sealed office buildings without operable windows, in which air quality depends on the capabilities of the building air handling equipment. Many people complain of eye irritation, mild illness, headaches and the like, which can usually be traced to pollutants in the indoor air. Since individuals' needs vary, a personal air purifier has provided means to achieve at least some individual control and improvement of air quality.
Existing desk top air purifiers are, however, plagued with problems. Most are excessively bulky and take up otherwise-needed desk space. In addition, the existing purifiers are noisy, only work properly in a horizontal position and deal poorly with cigarette smoke. In order for cigarette smoke to be removed effectively, the smoke must be captured near its source. To do this, careful attention must be paid to the configuration of the unit and to the air flow patterns of the unit. In particular, the behavior of exhaust air must be considered since the exhaust air must not interfere with the intake air.
Some of the important air flow considerations are as follows. First, a poorly located exhaust grille can cause incoming smoke to be blown away before it reaches an intake. Second, a high exhaust velocity can generate a Bernoulli effect wherein a region of negative pressure can form outside of the device, and thereby compete with the suction at the intake. This negative pressure phenomenon can be put to good use by arranging for incoming smoke to be directed by the negative pressure to an intake which is located to intercept the smoke along the way. For example, when an exhaust flow of reasonable velocity exits a device at or near desk level, rising smoke nearby has a tendency to move slightly downward due to the negative pressure of the exhaust. The smoke, therefore, can be diverted to a properly located intake. It should also be noted that the intake and the exhaust also must be separated by a sufficient distance. This avoids "short-circuiting" where the device intakes the majority of its own exhaust.
The present invention addresses each of these problems and provides for significant improvements because of particular unique features relative to prior art devices. The conventional desk top air purifier is generally a horizontally disposed box wherein intake air is received by a grille which extends upward for several inches in height from the surface on which the unit is placed. Treated air is then exhausted out the back. Cigarette smoke, which tends to rise by convection, also normally emanates from a height above the height of the intake of the purifier. The smoke, thereby, often misses the intake entirely to diffuses into the ambient air before purification. Much of the smoke, therefore, escapes to the upper reaches of the room to be recirculated without purification.